A Comprehensive Guide for Accurate Electrical Service Size Measurements | Electrical Service


For any kind of construction determining the appropriate electrical service size is a crucial step in designing a safe and efficient electrical system. Whether you are planning a new construction or renovating an existing electrical service, it is important to know how to calculate the required size. In this comprehensive guide by Emerge Electrical, we will look into the steps involved in calculating the electrical service size keeping in mind the electrical safety standards. 

Understanding Electrical Service Size

Team at Emerge Electrical is trained and competitive, knowing about everything electrical service size and here is our 9 step guide to understand it clearly. 

1: Identifying Connected Loads

The first step in calculating the electrical service size is to identify and quantify the connected loads. This involves making a comprehensive list of all the electrical appliances, devices, lighting fixtures, and other equipment that will be powered by the electrical system. A matching amperage value needs to be assigned to every item on the list.

2: Determining Load Diversity

Not all connected loads operate simultaneously at full capacity. To account for this, load diversity is taken into consideration. The possibility that no one linked load would run at maximum demand concurrently is known as load diversity. For example, lighting loads, HVAC systems, and kitchen appliances may have different usage patterns throughout the day.

3: Calculating Total Connected Load

Once the connected loads and their corresponding amperages are identified, the next step is to calculate the total connected load. Sum up the amperage values of all the connected loads to get an initial estimate of the electrical service size required.

4: Applying Demand Factors

Demand factors help to explain why not all connected loads run at maximum capacity at the same time. Different types of buildings and occupancies have recommended demand factors based on historical usage data. These factors are applied to the total connected load to determine the demand load.

5: Determining Service Factor

 The building’s characteristics and occupancy type are taken into consideration when calculating the service factor. Residential buildings typically have different electrical service factors than commercial or industrial buildings. It reflects the specific requirements and characteristics of the building and is used to further refine the demand load.

6: Calculating Diversity Factor

Diversity factor considers the probability that not all loads will be in use at the same time. It is a percentage that reflects the expected simultaneous operation of connected loads. Diversity factors are based on the experience and historical data specific to the type of building or occupancy.

7: Calculating Demand Load

The demand load is computed by taking the total connected load, multiplying it by the electrical service and demand factors, and dividing the result by the diversity factor. This formula helps determine the load that the electrical service must be designed to handle.

8: Determining Service Size

The right electrical service size must be chosen once the demand load has been computed. Service sizes are typically standardized, and the nearest standard size is selected based on the calculated demand load. Common residential service sizes include 100A, 200A, and 400A, while commercial and industrial services may require larger capacities.

9:Verification and Professional Review

It’s important to note that calculating electrical service size involves complex considerations and should ideally be verified by a licensed electrical professional. Consulting with an electrician or electrical engineer ensures that the calculations are accurate and compliant with local electrical codes and regulations.

Factors Influencing Service Size

Several factors influence the electrical service size you require. From the type of appliances you use to the square footage of your property, each aspect plays a role. To give you a comprehensive understanding of the factors at play, we’ll examine these in more detail. 

Emerge Electrical; The Expert Electrical Service in the Town! 

While a DIY approach in calculating electrical service is commendable, seeking professional consultation of Emerge Electrical is equally crucial. Contact us now and we’ll discuss the significance of involving experts in the field and how their insights can enhance the accuracy of your electrical service size calculation.


Calculating the electrical service size is a critical aspect of designing an electrical system that meets the demands of a building while maintaining safety and efficiency. By understanding the connected loads, applying demand factors, and considering diversity factors, one can determine the appropriate service size for a given application. However, it is crucial to recognize the complexities involved and seek professional guidance to ensure that the calculated service size aligns with industry standards and local regulations. Mastering the essentials of electrical service repair sizing is a fundamental step towards creating a reliable and safe electrical infrastructure.